Many display devices have limited color gamuts. Up until now, display manufacturers continuously attempted to increase the native gamut of the displays. However, there is an inherent conflict between the reduction of the power consumption and the increase of the color gamut and luminance of a display device, particularly in the case of portable displays. Increasing the color gamut requires the use of more chromatic filters (thicker filters), which in turn reduces the luminance of the display. In order to compensate for the reduction in luminance, a more powerful backlight is required, most often resulting in an increase in battery power consumption, which reduces the duration of operation of the battery and limits the overall performance of the product. Therefore, in those cases, the limited color gamut is the result of lowering the power consumption. In other cases, the display devices using certain technologies cannot have a large gamut.
Due to mismatch in color gamut, a display device may be able to display a color that cannot be reproduced by a printer; and the printer may be able to reproduce a color that cannot be displayed on the display device. Similarly, when an image produced from a scanner is displayed on a display device or printed on a printer, color losses may occur. To avoid such problems, a color management scheme can be used to match colors that can be represented on one device (e.g., a scanner or a display) to the colors on another device (e.g., a printer).
One of the problems associated with the small gamut display is that the color matching in a typical color management workflow produces poor results when a match is performed between the small gamut display and a destination device, which typically has a large gamut. For example, the quality of an image is reduced when a gamut compression is performed to match the gamut of a source device (e.g., a scanner) to the small gamut of the display in order to display the image on the small gamut display and when a gamut stretching is performed to match the small gamut of the display to a larger gamut of a destination device (e.g., a printer) in order to process the image on the destination device. Sometimes the colors of an image are designed on the screen, within the limited color gamut, before the colors are mapped into the larger gamut of a destination device for further processing (e.g., for printing). Even if the mapping is from one display device to another display device, stretching the smaller gamut into a larger gamut may impose serious problems.
Thus, in a color management workflow, color matching between a limited gamut device and an arbitrary device with a larger gamut will result in color losses due to mapping from a small gamut to a larger gamut. With various degrees, this situation exists on various computer systems, especially on portable computer systems using TFT LCD displays, which typically have a limited color gamut.
The current method of color characterization of a display device uses the chromaticity data of the primaries of the device. For example, Cathode Ray Tube (CRT) monitors have red, green and blue phosphors. The colors produced by the phosphors determine the colors of red, green and blue, the primaries of the CRT monitor. The positions of the primaries on a CIE (Commission International d'Eclairage) 1931 chromaticity diagram determine the color characteristics of the display device.
Typically, color matching operations through gamut processing (e.g., compressing, stretching, clipping and morphing) are performed to match the colors on a source device and a destination device. However, such color matching operations typically produce poor results when the difference in gamut is large and when the source gamut is small. For example, when printing an image displayed on a small gamut screen (e.g., a screen of a portable computer) using a printer with a large color gamut (e.g., a ink jet printer using photo quality papers), the colors can be attenuated and desaturated (washed out).